Machine for grinding the crank pins of crankshafts



May 28, 1940.

c. MAYER 2,202,111 MACHINE FOR A GRINDING THE CRANK PINS 0F CRANKSHAFTS Filed Nov. 23, 1958 4 Shets-Sheet 1 VIII Carl Mayer,

I f @543 s ea May 28, 1940. c. MA Y'ER 2,202,111 MACHINE FOR GRINDING THE CRANK PINS 0F CRANKSHAFTS 4 Sheets-Sheet 2 May 28, 1940.

c. MAYER 2,202,111 MACHINE FOR GRINDING THE CRANK PINS 0F CRANKSHAFTS Filed Nov. 23, 1958 .4 Sheets-Sheet s Car/Maya:

May 28, 1940.

c. MAYER 2,202,111

MACHINE FOR GRINDING THE CRANK PINS OF CRANKSHAFTS Filed Nov. 23, 1938 4 Sheets-Sheet 4 Ga r1 May l I I 31511 7 c J Patented May 28, 1940 UNITED STATES MACHINE FOR GRINDING THE CRANK PINS OF CRANKSHAFTS fr I Carl Mayer, Frankfort-on-the-Oder, Germany,

assignor to Rudolf Nolle, Berlin, Germany Application November 23, 1938, Serial No. 242,067 In Germany July 22, 1936 8 Claims.

This invention relates to a machine for grinding the crank pins for crank shafts and according to the invention the grinding is effected by the fiat front face of a grinding wheel having its axis perpendicular to the axis .of the bearing, the

crank shaft being rota-tably supported in adjusta'ble bearing clamps; the grinding wheel being arranged opposite the bearing clamps, the latter being. slidably mounted on a vertical support whereby the crank shaft is supported and ground in a vertical position.

By arranging the crank shaft in this manner a number of disadvantages of the hitherto usual horizontal arrangements are avoided and a number of considerably improved advantages are obtained. In particular, with crank pins which do not run true, it is possible to produce a finished precision grinding which, as regards quality, uniformity and accuracy, can otherwise only be at- 0 tained with large, heavy and consequently expensive precision grinding machines. By means of this invention, this result can be attained with a small, inexpensive, transportable, grinding machine which is easy to operate. This improve- '25 ment is obtained by the fact that, due to the Vertical position of the crank shaft the latter, throughout the movement necessary for satisfactory working, remains statically and dynamically balanced, and that also the smallest deflections due to its own Weight and deflections, which usually arise due to the alternating position relatively to the tool, are avoided. Moreover, by means of centerless grinding with simultaneous elimination of harmful bearing pressure on the supporting points in which the crankshaft is not only guided, but is also rotated, and finally, due to the fact that the irregularities usually caused by compensating weights and clamping tools are disposed with, the result is attained that non- 40 circular crank pins can bemade perfectly round by removing the minimum amount of material necessary for the purpose, i. e., by economical grinding, so that the old bearing can usually be used again, even without subsequent adjustment.

The crank shaft to be worked is, according to a further feature of the invention, set up for grinding purposes, on a rotatable face plate which not only rotates the crank shaft, but also lifts and lowers axially. The crank shaft then rotates (relieved of its own weight) in bearings, the dis- :tance between which is adjustable and which are sliclably arranged ona vertically disposed support.

It is known in circular grinding practice to mount the shaft to be groundin prismatic jaws and hitherto one of the two prism surfaces was grinding wheel, irregularities in grinding are un- This is due to the fact that initially Y avoidable. small depressions, for example, caused by careless positioning of the grinding wheel, become larger during further rotation and, as it were, always increase in size by a copying process. In other words, the depression caused in the first place by the grinding wheel exerts, after the shaft has turned through a reduced pressure on the diametrically opposite side of the shaft in pressing it against the grinding wheel, so that less material than actually necessary is removed at this point. Upon a further rotation through 180, a protuberance on the shaft being ground, comes to bear against'the counter-supportsurface, thereby causing an increased pressure to act in pressing the primaryv depression against the grinding wheel, which therefore causes this part of the shaft (which has already been recessed in error) to be further depressed. Byrepetition of this operation on the same diametrically opposite points, a crank pin is produced which has, on the 5 one side, a depression and, on the other side, a convex protuberance or bump.

If the counter-support element (prism) which canalso be in the form of a roller--is so turned or displaced that the supporting line no longer lies in the plane formed by the axis of the crank pin and the line of contact of the' is always essential for holding the crank pin, so

that polygonal crank pins are produced in the grinding operation instead of round ones.

Consequently, the new theory consists in that the point of support is only displaced by a few degrees from the plane formed by the center line of. the crank pin and the line of contact of the grinder, preferably by about 2 to 10.

For a rapid and certain setting up of the crank shafts to be ground, with the upright arrangement of the machine, the bottom end of the crank shaft stands in a driving device on a lifting plate which at the same time also imparts the turning movement to the crank shaft. This driving device is conveniently mounted to slide radially in the driving disc, with the result that the driving device can immediately adjust itself to the crank stroke of the crank shaft being worked, as well as to the small movements which the crank shaft carries out in the bearing at the commencement of the grinding due to its initial inaccuracy.

With crank shafts having only one crank pin bearing, as in single-cylinder engines or engines having oppositely moving pistons, and also with crank shafts having a. plurality of cranked portions, none of which lie in the same plane as the others, i. e., the crank shaft .of the Ford V-8 engine, the driving and supporting of the end crank pin of the crank shaft is effected by means of an extending angle member which replaces the second missing bearing. In this case, one of the outside main bearings is placed in the angle prism, which is slidably mounted on the lifting plate. It is possible in this way to insure an exactly vertical position of the crank shaft with respect to the lifting plate. If the crank pin to be ground is now placed in the suitably adjusted bearing clamp, the sliding angle prism also adjusts itself to the corresponding stroke. After adjustment has been made, it is still not necessary to fix the angle prism to the faceplate.

With earlier types of crank shafts, long lubricating grooves are frequently provided in the crank pin surface. With centerless grinding using bearing clamps, these grooves cause surface irregularities, because the groove, as it passes the line of support, causes a deflection .of the crank pin in the bearing clamp and thus a thickening at the diametrically opposite side where grinding is taking place; thus, by the copying operations. irregularities arise during the grinding.

In order to avoid such grinding errors, it is proposed to provide a third supporting surface (corrective support). There are provided three lines of support for the revolving cylindrical crank pin, of which those disposed opposite the grinding disc cooperate in such a manner that one can always become inoperative, i. e., each time that a lubricating groove passes it, without the position of the axis of the crank pin being altered thereby.

The third point of support is conveniently constituted by an interchangeable hard rubber or fiber plate. If it is not required, for example, with crank shafts not having a lubrication groove, the fibre plate is replaced by a felt plate with the result that this continuously keeps the grinding dust away from the supporting surface in the bearing clamps.

In order that the invention may be more clearly understood, two particular embodiments of the machine made in accordance therewith will now be described with reference to the accompanying drawings wherein Figure 1 is a part elevational and part sectional View of one embodiment with a crank shaft set up on the rotatable table or face plate.

Figure 2 is a plan view of the grinding device on the line IIII of Figure 1.

Figure 3 is a similar view on the line IIIIII of Figure 1, showing the adjustable and displaceable mounting with a measuring dial, and

Figure 4 is a longitudinal section through another form of grinding machine base, with the drive for the face plate and an adjustable eccentric for raising and lowering the face plate.

Figure 5 is a part elevational and part sectional View of a further embodiment of the centerless grinding machine for the grinding of crank pins in the vertical position with a driving device displaceable radially in the face plate.

Figure 6 shows the same face plate in side elevation.

Figure 7 is an elevation of a face plate having a radially displaceable angle prism for defining the vertical portion of a crank shaft which is guided at one place at its upper end.

Figure 8 is a plan view of a grinding device on the line VIII-VIII of Figure 5 and having a counter-support surface arranged out of parallel with the flat working face of the grinding body.

Figure 9 shows on an enlarged scale the parts of the grinding device shown in Figure 8 and which are arranged around the crank pin to be ground, and

Figures 10 and 11 each show a diagrammatic horizontal section through a crank pin in the grinding position with the novel arrangement of the counter-support roller and counter-support surface, respectively.

Referring to these drawings the grinding machine comprises a supporting pillar I', mounted on a base 2 and rotatable table or plate 3 displaceably mounted in a bearing bush 4 provided with worm gearing driven from a motor 5, said bearing bush 4 setting the face plate 3 in slow rotation. The face plate 3 includes a pin 3' reciprocally mounted in the bearing bush 4 so that the pin in the bearing bush 4 and the face plate can be reciprocated in a vertical plane in the bush 4 during the turning movement. In the embodiment according to Figure 1, this reciprocating movement is effected manually by means of a lever 6 through the linkage I actuated from a handle 8 at the top of the pillar I. According to Figures 4 and 5, the raising and lowering of the crankshaft 9 is effected automatically with the turning movement and to assist such movement a counter-weight I0 is provided in order to facilitate the raising and lowering of the crank shaft 9.

As illustrated in Figure 4, an adjustable eccentric 23 is driven by the motor 5 through a worm 2i and a worm wheel 22 so that, through the lever 24 the upward and downward reciprocating movement of the face plate takes place simultaneously with the actuation thereof.

In Figure 5, the adjustable eccentric is also indicated by the reference numeral 23. In this case, it acts directly on the pin of the face plate and, by means of a gearing connected with the hand-wheel 36, is exteriorly adjustable according or carriage [3. The entire grinding assembly (motor, spindle and grinding wheel) is so arranged that the mean axis of the spindle I5 is displaced relatively to that of the crank shaft 9, and the grinding line of contact is formed by a chord of the grinding wheel. The spindle is mounted without play at more than one point and is directly driven at the upper end through a flexible coupling from the high-speed motor I 4. One of the two supports carries a measuring gauge I! of approved type for controlling the grinding operation.

The exact adjustment and alignment of the crank shaft 9 is attained by suitable adjustment of the slidable bearings lB-l9 which are arranged at an angle of 45 to the bracket ll--|2. The supports 20 retain the crank shaft in the bearing clamp. During the grinding of the crank pins, the rotating crank shaft 9 is, as previously described, simultaneously reciprocated in a vertical plane so that the entire surface of a crank pin is contacted by the grinding wheel which remains in one position.

As will be seen more particularly from Figure 2, the supporting bracket l2, including the grinding device l8, 13, I4, I5, l6 carried thereby, are mounted on a stationary rigid plate-like frame element which closely surrounds the crank pin over about half of its circumference, and from the inner edge of which the operating parts acting upon the crank pin being ground, i. e., the grinding wheel I6 and the counter-support checks 13, project only a short distance, and on the inner walls of which the first internal mounting of the grinding spindle I5 is already provided.

Figures 10 and 11 show two different embodiments having counter-support rollers r r 1 and counter-support surfaces g g g respectively, and show the manner in which intensification of small irregularities of the bearing a can be avoided by lateral displacement of the countersupport line which is exactly opposite the grinding line a, into a slightly lateral position 0 If the line of counter-support c of the steady roller 1' is disposed diametrically opposite the line of grinding a, as was always the case hith erto, thetwo radial connecting lines m, n from the center point b of the crank pin to the line of grinding a on the one hand, and to the line of counter-support on the other hand, form an angle of 180, or if the surface g extends parallel to the working face 24 of the grinding wheel it, and if a depression has been formed onthe surface of the crank pin 2, for example by careless setting of the grinding Wheel 46, then after the crank pin a has turned through 180, this depression causes a protuberance to be formed on the diametrically opposite side of the crank pin 2, and this protuberance, after the crank pin .2 has rotated through a further 180 to the position of the original depression, causes a further depression at the same place, and this is repeated with each half revolution.

This disadvantage is eliminated by the steady or counter-support roller r which originally was kept as far as possible exactly opposite the printing wheel, being displaced laterally to about T2, i. e., to the angle --180or by the counter-support surface g originally kept parallel to the working face of the grinding wheel, being not at an angle by a few degrees, so that it assumed substantially the position Q The errors hereinbefore referred to can then no longer become bigger, but are distributed over the entire surface of the crank pin so that, finally, the latteragain becomes absolutely round.

As will be seen from Figures 5 and 6, the driving device, in the form of a center pin 35, is mounted to slide radially in the driving disc 3, said center pin 35 being fixed on a slide which, in turn, is freely displaceable in a radial groove 35 formed in the face plate 3.

In the embodiment according to Figure 7, an angle prism 38 is employed as the driver instead of the center pin. The crank shaft 9, which is placed in a bearing clamp, is held in the single prism 38 by one of its end crank pins.

Finally, according to Figures 8 and 9, three supporting points 3!, 32, 33 are provided on the machine opposite the grinding wheel I6. Two of these points (3!, 32) serve as usual for the accurate alignment of the crank shaft, whereas the third (33) acts as an auxiliary supporting point merely for maintaining the adjusted position of the crank pin when the other supporting point 3| becomes temporarily inoperative, for example, when a longitudinal lubrication groove is provided in the crank pin and just when this groove, during rotation of the crank pin, passes the normal point of support 3|.

Having now particularly shown and described the nature of the said invention and in what manner the same is to be performed, I declare that what I claim is:

I claim:

1. A machine for grinding the crank pins of crank shafts by means of the flat front face of a grinding wheel having its axis perpendicular to the axis of the bearing, in which the crankshaft rotates in adjustable bearing clamps, and in which the grinding wheel is positioned opposite a bearing clamp, a vertical support, said bearing clamps being slidably mounted thereon, a face plate for support of the crank shaft, means for turning and lifting the face plate, and means adjusting the degree of lifting movement according to the width of the crank pin to be ground.

2. A machine according to claim 1, characterized in that the grinding wheel is adjustable during grinding in the direction of its rotation axis.

3. A machine of the character described comprising a base, a vertical support thereon, a pair of brackets vertically adjustable on the support, a plate-like frame on the brackets having means for closely embracing a crank pin over approximately one-half its circumference, grinding means on the plate and projecting slightly from the inneredge of the plate, means for actuating the grinding means, a rotatable face plate carried by the base, means for raising and lowering the face plate, and said face plate having driving and support means for a crank shaft.

4. A machine according to claim 3, characterized in that the driving device is mounted for radial adjustment in the face plate.

5. A machine according to claim 3, characterized by a driving device in the form of an angle prism, in which the crank shaft, placed in a bearing clamp, is secured by one of its free end crank pins.

6. A machine for grinding the crank pins of crank shafts by means of the flat front face of axis, and eccentric means for turning and lifting the face plate.

other hand bisect the plane of rotation of the crank shaft in planes at an inclination of a few degrees relatively to one another.

ranged with its axis parallel to the crank shaft 8. The structure of claim l in which one of said bearing clamps comprise a three point support means positioned opposite the grinding wheel,

two of which act for exact alignment of the crank shaft, and'the third functioning as an auxiliary supporting point for maintaining a fixed position when one of the other two supporting points becomes temporarily inoperative.

CARL MAYER. 

